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Determinants of variation between Fick and indicator dilution estimates of cardiac output during diagnostic
Insights
The Fick and dye methods for measuring cardiac output show no systematic differences in patients with cardiovascular diseases. Dye cardiac output is valid across varying cardiac indices and valvular regurgitation levels.
Area of Science:
- Cardiology
- Cardiovascular Physiology
Background:
- Accurate measurement of cardiac output is crucial for managing cardiovascular diseases.
- Both Fick and dye dilution methods are commonly used but have shown variability.
Purpose of the Study:
- To compare simultaneous Fick and duplicate dye cardiac output measurements in patients with cardiovascular diseases.
- To assess the validity of the dye dilution method under various physiological conditions.
Main Methods:
- Simultaneous Fick and duplicate dye cardiac outputs were performed in 105 patients during cardiac catheterization.
- Dye was injected into the pulmonary artery and sampled from the brachial artery.
- Patients included those with various cardiovascular diseases, including valvular regurgitation.
Main Results:
- 84% of dye cardiac outputs agreed within 10% of identity; 98% agreed within 25%.
- 75% of Fick and dye methods agreed within 20%, with individual variations from -27% to +58%.
- No systematic differences were observed between Fick and dye methods, even with low cardiac index or valvular regurgitation. Variation increased with higher cardiac index.
Conclusions:
- The dye dilution method, with pulmonary artery injection and brachial artery sampling, is valid across different cardiac indices and in the presence of valvular regurgitation.
- Variations between Fick and dye methods may be partly due to errors in oxygen difference and consumption measurements.
- The accuracy of the dye method depends on sufficient data points for semilogarithmic trace analysis.
Abstract:
Simultaneous Fick and duplicate dye cardiac outputs were done in 105 patients with various cardiovascular diseases during routine cardiac catheterization. Dye was injected into the pulmonary artery and sampled from the brachial artery. Nineteen patients had mitral and/or aortic valvular regurgitation. Eighty-four per cent of the duplicate dye cardiac outputs agreed within 10 per cent variation from the line of identity, and 98 per cent were within 25 per cent. There was no systematic difference between the Fick and dye methods. Seventy-five per cent agree within 20 per cent variation from the line of identity. However, individual variation ranged from -27 to +58 per cent. There was, also, no systematic difference between Fick and dye methods either with low cardiac index or valvular regurgitation. Variation between the two methods was less with low cardiac index and greater with higher cardiac index. The variation was not increased in the presence of valvular regurgitation. The variation in the two methods could partly be explained by errors in the measurement of arteriovenous oxygen difference and oxygen consumption. When the injection is made into the pulmonary artery and sampled from the brachial artery, dye outputs are valid irrespective of the level of resting cardiac index and valvular regurgitation as long as there are enough points to draw a straight line from semilogarithmic trace of the descending limb.